The use of shaving aids in combination with razor blades to provide lubrication benefits during the shave is known. See e.g., U.S. Pat. Nos. 7,121,754; 6,298,558; 5,711,076; 5,134,775; 6,301,785, U.S. 2009/0223057, US 2006/0225285, WO2007/031793 and U.S. Pat. No. 5,431,906. Such shaving aids typically comprise a water-insoluble matrix material to provide structural integrity and a water-soluble polymer, such as polyethylene oxide (polyox), in order to provide lubrication during the shave once the water-soluble polymer forms a solution with the water present during shaving. Since the introduction of polyox as a shaving lubricant, however little development has been made in the field, even though polyethylene oxide polymers are not without limitations. For example, the use of polyethylene oxide polymers having a low molecular weight only provides limited lubrication, and while improved lubrication may be seen when using polyethylene oxide polymer having higher molecular weights, this negatively impacts other aspects of the aqueous solution typically formed in-use. The resultant viscosity in aqueous solution may also increase, leading to negatively perceived attributes, for example concerning the feeling of the shave for the user, particularly in respect of the lubricant. The prior art does also describe the use of combinations of high and low molecular weight polyethylene oxide polymers in order to balance these performance attributes. Nevertheless, such combinations are also limited in their ability to improve performance and or suffer from other negative performance attributes. The art further describes the incorporation of additional materials to further improve the lubrication performance. For example U.S. Pat. No. 6,442,839 and US2007/0110703 describe the use of low levels of mineral and essential oils, butters, waxes and silicones. The use of mineral oil to enhance the glide performance is described in US2008/0060201. However the art also discloses that the presence of oils results in a reduction of the swelling and solubility of the shaving aid contained in water insoluble polymer matrix. The ability of the shaving aid to swell in contact with water is however believed to be the key mechanism by which the lubrication benefit is delivered to the skin. Hence this is not desirable, as it will negatively impact the overall performance. Thus oils are typically avoided in the matrix.
Another limitation of such shaving aids is related to the manufacturing process which typically involves an injection molding or extrusion process step. These processes require elevated temperatures in order to melt all the component materials and then subsequently mix them together and then injection mold or extrude. Consequently, the manufacture of such shaving aids is limited to low levels of additives and or materials which are not degraded by such process conditions. Nevertheless, the presence of even low levels of such additives in the manufacturing process can result in barrel slip and conveying inconsistencies which is also undesirable.
US2009/0223057 describes a razor shaving aid material that will last for an extended period of time and that can be manufactured at temperatures to avoid thermal degradation of ingredients, comprising a water soluble shaving aid, a water insoluble erodible medium that has a melting point above 45° C. and a molecular weight below 25000, wherein the water soluble shaving aid is soluble with the water insoluble erodible medium. The compatibility of the water soluble material and the water insoluble erodible material favorably influences the longevity of the shaving aid material. This manufacturing process is still complex however requiring multiple steps and component phase compatibility. Furthermore the improved longevity results in a shaving aid which is hard and brittle and which does not deposit sufficiently during use. Furthermore, the shaving aid is still also limited with regard to the addition of additives, which must also be compatible in the matrix.
Consequently there is still a need to provide a solid lubricating member for razor cartridges which can be manufactured in a simple one batch process comprising a water soluble polymer and a liquid phase contained therein exhibiting improved lubricating properties over a sustained period which can be readily manufactured without impacting performance due to thermal degradation of the ingredients and which can accommodate additional additives to provide desirable skin care benefits, especially in the liquid form such as oils.